49ers sign outside linebacker Haggans

The 49ers tried to address their lack of depth at outside linebacker in the draft when they spent two of their seven picks on the position.

Two knee injuries and four months later, youth hasn’t provided the answer.

In response, the 49ers turned to experience Sunday, signing former Cardinals outside linebacker Clark Haggans, 35, a 12-year veteran who is the oldest nonspecialist on the roster.

Prior to signing Haggans, who was released by Arizona on Friday, the 49ers had just three outside linebackers: Aldon Smith, Ahmad Brooks and Parys Haralson, whose availability for the regular-season opener at Green Bay on Sunday is in question. Haralson has missed the past two practices, and Jim Harbaugh has said he’s “working through something,” his stock response when asked about an injured player.

Injuries also befell fifth-round pick Darius Fleming, who suffered an ACL injury in May, and seventh-rounder Cam Johnson, who played in just one preseason game after having knee surgery in early June. He was signed to the practice squad Saturday.

Those injuries paved the way for the signing of Haggans, who started 16 games for the Cardinals last year and had 30 tackles and three sacks. Haggans has started 104 games, won a Super Bowl with the 2005 Steelers and ranks 29th among active players with 46.5 sacks.

Haggans could face a three-game suspension from the NFL in connection with a DUI arrest in 2011. His agent, Jeff Sperbeck, said there will be a hearing on the matter Wednesday, via phone. He hopes Haggans can avoid a suspension or have the discipline reduced.

Haggans, who was also convicted of DUI in 2004, posted a statement on Sperbeck’s Twitter account in June to explain the circumstances of his DUI conviction on April 21, 2011, in Chandler, Ariz.

Haggans said he rushed home from a concert after his babysitter called and said his 5-year-old daughter was having difficulty breathing. Unable to locate his wife at the concert, Haggans drove home and was cited for speeding, running a red light and “extreme DUI,” meaning he had a blood-alcohol content of at least 0.15.

In June, he spent two days in a Pennsylvania prison, where he also served a seven-day work release.

“In hindsight, I should have found another way home, and I take full responsibility for my actions,” Haggans wrote.

Haggans’ signing was confirmed by a league source. The 49ers have not announced which player has been released to make room for Haggans on the roster. They are expected to do so Monday.